Cathode-ray tube



May 28, 1946.'

c.` s. szEcal-loA CATHODE RAY TUBE Filed Nov. 15, 1945 Patented May 28, 1946 CATHODE-RAY TUBE Constantin S. Szegho, Chicago, Ill., assignor to The Bauland Corporation, Chicago, Ill., a corporation of Illinois Application November 13, 1943, Serial No. 510,130

Claims.

This invention relates to new and useful improvements in cathode ray tubes.

One object of the invention is to provide a cathode ray tube in which the cathode ray beam will cover a maximum useful area of the screen in a horizontal direction.

One of the important problems of the practical television art is to reduce th'e size of the receiving apparatus. The cathode ray tube constitutes va substantial part of the volume of a, television receiver. Since a tube having a circular screen is wasteful of space, it has been suggested to make the end of the tube substantially rectangular, with an aspect ratio of four to three, and to shape the bulbso that its cross-sections are all smaller in area than the rectangular screen provided at the end of the tube.

However if the distance between the electron gun and the screen is small, i. e. if the tube is made sulcienaly short so as to fit within a reasonably small cabinet, then diculties arise in providing sufcient power for scanning in the horizontal or high frequency direction.

In accordance with the present invention, the magnetic eld strength' for controlling horizontal scanning is better utilized in tubes of the above-described type by reducing the diameter of the tube neck around which the defiectors are located, as compared to the diameter that one would obtain with a tube neck having a circular cross-section.

The invention will be described in greater detail with reference to the drawing in which:

Fig. 1 is the side elevation of a cathode ray tube;

Fig. 2 is a vertical cross-section of a tube neck of circular cross-section;

Fig. 3 of a tube neck having an elliptical crosssection; and

Fig. 4 of a tube having a substantially rectangular cross-section.

In Fig. 1: I is a cathode ray tube; 2 is the screen thereof; 3 is the neck, housing the usual electron gun; and 4 is the horizontal magnetic deflecting coil.

The maximum angle of deflection a, is limited by the geometry of the neck 3. If the deflection angle becomes larger than a, then the electron beam 5 will impinge on the forward edge E 0f the neck 3. If the diameter of a circular neck, such as that shown in Fig. 2, be increased to permit a wider swing for the electron beam, then this Would necessitate wider spacing of the deilecting coils 4 and, therefore, would cause the reduction of the magnetic field strength to a point where it could not swing or properly control a cathode ray beam displaying a given resistance to deilection from a straight path.

However if, accordance with this invention and as shown in Figs. 3 and 4, the cross-section of the neck 3 is made elliptical or rectangular, then the magnetic eld, which is approximately inversely proportional to the distance h, will remain constant but the angle of deection a, which is proportional to the dimension Z, of the cross-section of the neck, is increased as compared to the tube neck shown in Fig. 2. If cathode ray tubes having rectangular screens are used, then the dimension l of the cross-section of the neck will be in a horizontal direction and the dimension h in the vertical scanning direction.

While I have shown as examples of my invention certain geometrical shapes of neck and screen, it is to be understood that this invention is not limited to such particular shapes or relative dimensions, but this invention is applicable to all cases wherein the aspect ratio of the reproduced image differs from unity.

What is vclaimed is:

1. A cathode ray tube having a neck of elliptical cross section for deflection control and a screen geometrically similar to the cross section ci the neck.

2. In a cathode ray device, a cathode ray tube according to claim 1, and deection means at the neck for scanning the screen in the direction of the greater axis of the ellipse.

3. In a cathode ray device, a cathode ray tube according to claim l, and deflection means for scanning the screen in the direction of the greater axis of the ellipse including a magnetic deflection coil having two oppositely disposed portions situated parallel to the greater diameter of the elliptical cross section of the neck.

4. A tube according to claim 1, and in which the tube extending from the neck to the screen is of substantially frusto-conical form.

5. A tube according to claim Land in which the neck is of substantially cylindrical extension and the tube portion extending from the neck to the screen is of substantially frusto-conical form.

CONSTANTIN S. SZEGHO 

